Electron discharge tube



Feb-27, 1940. B. o. M. GM ET AL 2,191,884

ELECTRON DISCHARGE TUBE Filed May 21, 1937 v sARN/iwfl M. GALL l.lAN BART HUGENHOLT.

ATTORNEY Patented Feb. 27, 1940 ,e I

1 UNITED STATES PATENT, oF ioE ELECTRON DISCHARGE TUBE Bernardus Octavianus Maria Gall-and Jan Bart Hugenholtz, Eindhoven, Netherlands, .assigners, by'inriesne assignmentato Radio rporationmof America, New York, N. Y., a corporation of Delaware Y I I Application May 21'; 1937. Serial No. 143,898

' Inthe Netherlands June 22, 1936 4 Claims. (Cl. 250-275) Theinvention relates to electron discharge its conductors" behind and in alignment with tubes equipped with an electrode system which the conductors of the screen grid in planes percomprises several grid-like electrodes, at least pendicular to the cathode, viewed in a direction one of which is a screen grid. from the cathode to the anode. When the auxa In tubes having aplurality of grid-like eleciliary grid is at zero or negative potential with trodes, for example in the so-called screen grid reference to the cathode, there is obtained in tubes, the grid-like electrodes are usually so the neighborhood of the screen grid a field diswound in order to meet the requirements when tribution such that regardless of how another these electrodes are utilized in diiferentcircuit grid located close to the cathode, for example it arrangements, thatone grid is-of asmallpitch, the control grid, may loe wound, the electron 1 another grid of larger pitch and, for example, stream does not 'strikethe conductors of the a further grid of variable pitch. The consescreen grid, or' strikes to only a very slight ex quence is that a large proportion of the electent. Although from an electrical and constructrons do not flow directly to the anode, but tional point of View the simplest way to mainii) may be intercepted by the several grids, partain the auxiliary grid at the desired potential ticularly by those grids which have a positive is to connect it within the tube to the cathode, potential such, for example, as the screen grids. it is possible to connect the auxiliary grid to As is well known, the screen grid currents thus a point of zero potential outside the tube, or to produced may cause, for example, in high freconnect it. either inside or outside the tube to go quency amplifying tubes various harmful phea point of negative potential such as the con: nomena such as the efiect often known asrustrol grid. Furthermore, any other grids present fi in the tube may to advantage be of the same The suggestion has been made that the screen pitch and be mounted between the screen grid grid current may be minimized by arranging the and the anode with their respective conductors 3;, conductors of two or more of the grids in the in alignment with the conductors, of the screen tube in alignment or behind oneanother in grid in planes perpendicular to the cathode viewed planes perpendicular to the cathode when viewed in a direction from the cathode to the anode. in a direction from the cathode to the anode. The invention is not limited to those discharge Although this construction permitsappreciable tubes in which only one control grid is located on reduction in the screen grid current, such tubes between a screen grid and the cathode, but may in some cases have considerable disad may also be utilized in discharge tubes provantages of a constructional nature, particularly vided with a so-called space charge grid. The inif the tubes have a large number of grid-like vention may also be embodied in tubes such as electrodes, of which the first grid closest to the hexodes, octodes, etc., in which one or more I 3.3 cathode is of small pitch and is wound very oscillator grid-like electrodes are located betightly, and the pitch of the other grid electrodes tween the screen grid and the cathode and in has to conform to that of the first grid. which a plurality of screen grids may be present The principal object of this invention is to in the tube. 7 provide a multigrid tube which has a screen or The invention will be understood more easily 49 other positive grid preceded by a control or by reference to the accompanying drawing which similar grid of difierent pitch and nearer the shows diagrammatically the arrangementof the cathode and in which the current to the positive electrodes of an electric discharge tube accordgrid is minimized. 7 ing to the present invention.

Another object is to provide a screen grid type The drawing shows diagrammatically a screen of tube which has a control grid of smaller pitch grid type of tube having an indirectly heated 45 than the screen grid and in which the screen cathode I consisting of a tubular cathode, inside grid currentis substantially no greater than in of which is a heating element insulated from a screen grid tube having a control grid and a the cathode, and several tubular'cold electrodes screen grid of the same pitch with the con coaxial with the cathode, such asa control grid ductors in alignment. 2, a screen grid 3, and an anode 4. Between the 50 In accordance with the present invention, a control grid and the screen grid and insulated tube comprising a system of electrodes among from both of said grids. is located an auxiliary which there is at least one screengrid has at grid 5 which is conductively connected to the a short distance in front of and on the cathode cathode and whichhas been wound in such manside of the screen grid an auxiliary. grid with ner that, viewed in a direction from the cathode 5 to the anode, its turns and those of the screen grid are located behind one another in planes perpendicular to the cathode, owing to which a field distribution is obtained which causes no electrons or only a slight number to strike the screen grid.

I claim:

1. An electron discharge tube comprising a cathode, an anode, a plurality of grids interposed between said cathode and said anode to be passed in succession by the electron stream from said cathode to said anode, and including a control grid adjacent the cathode and a pair of said grids of the same pitch and electrically insulated from each other being mounted side by side with their respective conductors aligned normal to said cathode between the control grid and the anode, and a direct electrical connection between said cathode and that grid of said pair which is nearer said cathode.

2. An electron discharge tube having an electrode system comprising a cathode, an anode, a screen grid interposed between said cathode and said anode, another grid between said screen grid and said cathode of a pitch difierent from the pitch of said screen grid, and an auxiliary grid of the same pitch as said screen grid interposed between and insulated from said screen grid and said other grid with its conductors aligned normal to said cathode with corresponding conductors of said screen grid.

3. An electron discharge devicecomprising a cathode, an anode, and three grids interposed between and at difierent distances from said cathode and said anode to be-passed in succession by an electron stream from said cathode to said anode, the two of said grids moreremote from the cathode being insulated from each other and having equal numbers of spaced conductors, with each conductor of each grid in alignment between said cathode and said anode with a corresponding conductor of the other grid, and a direct connection between said second grid and said cathode.

4, An electron discharge device having a cathode and an anode and a plurality of helical grids between said cathode and said anode and including a control grid, a screening grid between the control grid and the anode, and an additional screening grid between the first-mentioned screening grid and control grid, the screening grids having the turns aligned with respect to each other, said first screening grid being adapted to be maintained at a positive potential with respect to the cathode during operation of the tube and said additional screening grid being maintained at substantially cathode po- 

